This invention relates to the polymerization of olefins and more particularly to catalysts used therefor.
The invention has for its primary object to provide an improved process for polymerizing various olefins in the presence of a composite catalyst comprising transition metal halides constituting the Ziegler catalyst effectively carried on magnesium oxide through the medium of organic halides and organoaluminum compounds or alkylzinc whereby polymer yields based on both carrier and transition metal are notably increased with ash contents in the polymer held to an absolute minimum, thus eliminating the necessity of separate steps for the removal of residual catalysts.
In polymerization processes of this character, attempts have been made to provide enhanced polymer yields by the use of titanium tetrachloride carried on magnesium oxide as disclosed in Belgian Pat. No. 705,220, or by the use of titanium tetrachloride carried on magnesium oxide which has been treated with halogenating agents such as hydrogen chloride, trichlorophosphorus monoxide (POCl.sub.3) and dichlorocarbon monoxide (COCl.sub.2) as shown by Japanese Patent Publication No. 47-14084. The use of such halogenating agents involves complicated handling and invites considerable corrosion of the equipment. Another disadvantage of these prior art processes is that while the yield of polymer based on the transition metal is sufficient, that based on the carrier is not satisfactory.
It has now been discovered that the use of certain organic halides (characteristically different from the above halogenating agents), when admixed with magnesium oxide and transition metal halides and heated together at prescribed temperatures, will contribute to increased activity of the polymerization of olefins when carried out in the presence of an organometal compound, with a remarkable increase in polymer yield based on both carrier and transition metal and further with greater bulk density of the resulting polymer. It has also been found that the polymerization process according to the invention will provide better activity particularly based on the carrier and less residual ash in the polymer than obtainable by the aforesaid prior art processes.